1. Field of the Invention:
This invention relates to a clay mineral sheet, which can be effectively used as, for example, intermediates between members, such as gasket and packing.
2. Description of the Prior Art:
There are clay mineral sheets composed mainly of a flaky clay mineral, such as mica and montmorillonite. Only a very thin sheet is, however, available in order to obtain the necessary flexibility. There are also known heat resistant sheets composed mainly of fibrous substance, such as asbestos, glass fiber and sepiolite. They, however, have a low modulus of elasticity along their thickness or poor creep resistance. Moreover, fibrous materials are often expensive or difficult to obtain. There are also known sheets composed mainly of organic compound elastomer (rubber) and sheets composed mainly of graphite in the form of scales. However, organic compound sheets have poor heat and oil resistances, and graphite sheets are very expensive although they have required properties of a heat-resistant gasket or the like.
There is also a rigid foam or sheet formed of swollen vermiculite and a water-stable additive, or a sheet material in the form of a fibrous web containing exfoliated vermiculite. However, the conventional materials do not concurrently possess high flexibility, high tensile and compressive strength, excellent recovery and other properties required for gaskets or the like.